Control valve unit for hydraulic actuator

Abstract

A control valve unit (10) disclosed supplies hydraulic fluid to an actuator (12) in a manner that controls both acceleration and deceleration of the actuator movement. A supply valve (14, 22) of the unit is movable from a central closed position in opposite directions to open positions and back to the closed position by a servomechanism (16) and a control circuit (18) that operates the servomechanism to cooperatively control the supply of the hydraulic fluid to the actuator in a manner which controls both acceleration and deceleration of the actuator movement. A control member (62) of the servomechanism operates the supply valve and is moved in a controlled manner by cooperative operation of a pair of hydraulically operated pilot pistons (88a, b), a pair of acceleration control pistons (90a, b), and a pair of deceleration cams (84a, b). Directional and flow control valves (89, 92) of the control circuit operate the pilot pistons and the acceleration control pistons in cooperation with each other. Velocity governors (197) are also provided.

What is claimed is: 
     
       1. A control valve unit for a hydraulic actuator, the unit comprising: a supply valve that is movable from a central closed position in opposite directions to open positions so as to supply hydraulic fluid to the actuator in order to selectively actuate movement thereof in opposite directions; a mechanical servomechanism including a control member and a pair of deceleration cams for moving the supply valve to its central closed position so as to terminate the supply of hydraulic fluid to the actuator upon movement thereof to opposite extremes of travel; and a hydraulic control circuit including a pair of pilot pistons that are alternately supplied hydraulic control fluid to move the control member and hence move the supply valve in one direction or the other to one of its open positions in order to commence movement of the actuator in an associated direction, and the control circuit also including a pair of acceleration control pistons that engage the control member to control the opening movement of the supply valve by the pilot pistons, whereby the servomechanism and control circuit cooperatively control acceleration and deceleration of the actuator movement. 
     
     
       2. A unit as in claim 1 further including at least one restricted opening for limiting hydraulic fluid flow in order to limit movement of the acceleration control pistons. 
     
     
       3. A unit as in claim 2 wherein the restricted opening has an adjustable size to thereby permit adjustment of the level of actuator movement acceleration. 
     
     
       4. A unit as in claim 1 wherein the control circuit further includes: a directional valve for selectively supplying hydraulic control fluid to one or the other pilot pistons in order to move the control member and thereby commence opening of the supply valve and accompanying movement of the actuator in an associated direction; and   a flow control valve that limits hydraulic control fluid flow from the acceleration control pistons to govern movement of the control member and thereby control acceleration of the actuator movement.   
     
     
       5. A unit as in claim 4 wherein the flow control valve includes a pair of restricted openings of adjustable size through which hydraulic fluid from the acceleration control pistons is forced to control the actuator movement acceleration. 
     
     
       6. A unit as in claim 5 wherein the flow control valve includes check valves respectively associated with the restricted openings, a passage that extends between the directional valve and the check valves, and a pair of passages respectively extending between the check valves and the acceleration control pistons. 
     
     
       7. A unit as in claim 1 wherein each pilot piston includes first and second ends that are movable with respect to each other in an extendable and retractable manner, and each piston also including a spring that biases the ends thereof in an extending direction. 
     
     
       8. A control valve unit for a hydraulic actuator, the unit comprising: a supply valve that is movable from a central closed position in opposite directions to open positions so as to supply hydraulic fluid to the actuator in order to selectively actuate movement thereof in opposite directions; a mechanical servomechanism including a control member and a pair of deceleration cams for moving the supply valve to its central closed position so as to terminate the supply of hydraulic fluid to the actuator upon movement thereof to opposite extremes of travel; and a hydraulic control circuit including a pair of pilot pistons that are alternately supplied hydraulic control fluid to move the control member and hence move the supply valve in one direction or the other to one of its open positions in order to commence movement of the actuator in an associated direction, each of said pilot pistons including a piston end and a plunger end slidably supported in an extendable and retractable relationship with respect to each other, each pilot piston also including a spring that biases the piston and plunger ends thereof away from each other so as to provide a bias that engages its plunger end with its control member, the control circuit also including a pair of acceleration control pistons that engage the control member to limit the control member movement that opens the supply valve under the impetus of the pilot pistons, and the control circuit also including a directional valve for operating the pilot pistons and a flow control valve for operating the acceleration control pistons, whereby the servomechanism and control circuit cooperatively control acceleration and deceleration of the actuator movement. 
     
     
       9. A control valve unit for a hydraulic actuator, the unit comprising: a supply valve that is movable from a central closed position in opposite directions to open positions so as to supply hydraulic fluid to the actuator in order to selectively actuate movement thereof in opposite directions; a mechanical servomechanism including a control member and a pair of deceleration cams for moving the supply valve to its central closed position so as to terminate the supply of hydraulic fluid to the actuator upon movement thereof to opposite extremes of travel; and a hydraulic control circuit including a pair of pilot pistons that are alternately supplied hydraulic control fluid to move the control member and hence move the supply valve in one direction or the other to one of its open positions in order to commence movement of the actuator in an associated direction, each of said pilot pistons including a piston end and a plunger end slidably supported in an extendable and retractable relationship with respect to each other, each pilot piston also including a spring that biases the piston and plunger ends thereof away from each other so as to provide a bias that engages its plunger end with the control member, the control circuit also including a pair of acceleration control pistons that engage the control member to limit the control member movement that opens the supply valve under the impetus of the pilot pistons, a directional valve for selectively supplying pressurized hydraulic fluid to either pilot piston in order to retract the ends thereof relative to each other in order to compress its spring and thereby move the control member to one of the open positions against the bias of the other pilot piston, and a flow control valve having a pair of restricted openings of adjustable size through which the acceleration control pistons respectively force hydraulic fluid to limit the control member movement under the impetus of the pilot pistons, whereby the servomechanism and control circuit cooperatively control acceleration and deceleration of the actuator movement. 
     
     
       10. A control valve unit for a hydraulic actuator, the unit comprising: a valve block; a supply valve having a spool that is movable within the valve block from a central closed position in opposite directions to open positions so as to supply hydraulic fluid to the actuator in order to selectively actuate movement thereof in opposite directions; a mechanical servomechanism including a pair of deceleration cams, a rocker moved by the deceleration cams at opposite extremes of the actuator travel, and a cradle mounted on the valve block and moved by the rocker so as to move the spool of the supply valve to the central closed position thereof in order to terminate the supply of hydraulic fluid to the actuator; and a hydraulic control circuit including a pair of pilot pistons that are alternately supplied hydraulic control fluid to move the cradle and hence move the supply valve spool in one direction or the other to one of its open positions in order to commence movement of the actuator in an associated direction, each of said pilot pistons including a piston end and a plunger end slidably supported in an extendable and retractable relationship with respect to each other, each pilot piston also including a spring that biases the piston and plunger ends thereof away from each other so as to provide a bias that engages its plunger end with the cradle, the control circuit also including a pair of acceleration control pistons that engage the cradle to limit the cradle movement that opens the supply valve spool under the impetus of the pilot pistons, a directional valve for selectively supplying pressurized hydraulic fluid to either pilot piston in order to retract the ends thereof relative to each other in order to compress its spring and thereby move the cradle to one of the open positions against the bias of the other pilot piston, and a flow control valve having a pair of restricted openings of adjustable size through which the acceleration control pistons respectively force hydraulic fluid to limit the cradle movement under the impetus of the pilot pistons, each restricted opening of the flow control valve having an associated check valve, and passages in the valve block that communicate the piston ends of the pilot pistons with the check valves such that extension of the pilot pistons supplies hydraulic fluid through the associated check valve to the associated acceleration control valve to provide engagement thereof with the cradle, whereby the servomechanism and control circuit cooperatively control acceleration and deceleration of the actuator movement.